1. Field of the Invention
The present invention relates to an improvement in a scroll type fluid machine to be used e.g. as a compressor, an expander, etc.
2. Description of the Prior Art
Scroll type fluid machines, having the ability to operate with a high efficiency and low noise, are used in large numbers as compressors for air conditioning and refrigeration purposes.
Generally, such a scroll type fluid machine e.g. a scroll type compressor, has a compression portion 3, as shown in FIG. 4, in which a stationary scroll 1 and a swivel scroll 2, in a pair, are engaged with each other.
More concretely, the stationary scroll 1 has an end plate 4 and a spiral wrap 5 provided projectingly from the inner face of the end plate 4. The swivel scroll 2 likewise has an end plate 6 and a spiral wrap 7 provided projectingly from the inner face of the end plate 6. These wraps are engaged with each other with a predetermined phase.
The stationary scroll 1 is fixed to a frame 10 provided e.g. within a hermetic casing 9, and the swivel scroll 2, with the back face of its end plate 6 being directed downwardly, is supported on the frame 10 via a thrust bearing 11.
The central portion of the back face of the swivel scroll 2 is connected to a drive source, such as a rotational shaft 13 of an electric motor 12, provided within the hermetic casing 9 so that the swivel scroll in its entirety is driven to make revolutional swivel motions around the central axis of the stationary scroll 1. More concretely, at the shaft end of the rotational shaft 13, there is provided an eccentric pin 14 to be fitted rotatably in the central portion of the end plate of the swivel scroll 2, and by the rotation of the electric motor 12, the swivel scroll 2 is driven to make revolutional swivel motions relative to the stationary scroll 1.
The scroll type compressor compresses work by the swivel scroll being driven by the electric motor 12 to make swivel motions. That is, a plurality of compression chambers. 15 are formed between the wraps and move to gradually reduce their volumes while moving from a suction port 16 disposed on the outer side of the wrap 5 to a discharge port 17 disposed at the center of the wrap 5.
In such a scroll type fluid machine, in order to operate, there is provided an Oldham ring 18 between the end plate 6 of the swivel scroll 2 and the frame 10, as shown in FIG. 5, for prohibiting rotation of the swivel scroll 2.
The Oldham ring 18 is conventionally constructed so that it has a ring portion 19, as shown in FIG. 6, located between the end plate 6 of the swivel scroll 2 and the frame 10. At two places where a diametrical line of the ring crosses the ring portion 19, two swivel side keys 20, 20 are formed, in a pair, projecting from the end faces of the ring portion 19 as an integral body with the ring portion 19. At two places of the ring portion 19 on a diametrical line perpendicularly crossing the diametrical line, two stationary side keys 21, 21 are formed, in a pair, projecting from the opposite end faces of the ring portion 19 as an integral body with the ring portion 19.
The swivel side keys 20, 20 are fitted slidably in key ways 22 formed extendingly in the diametrical direction on the back face (lower face) of the end plate 6 of the swivel scroll 2 and the stationary side keys 21, 21 are likewise fitted slidably perpendicular to key ways 23 formed extending in the diametrical direction on the upper face of the frame 10.
Thus, upon rotation of the rotational shaft 13, the swivel side keys 20, 20 reciprocally displace in the direction of arrows A (FIG. 6) within the key ways 22. The stationary side keys 21, 21 reciprocally displace in the direction of B (FIG. 6) within the key ways 23, thus the swivel scroll 2 makes revolutional swivel motions, without making rotational motions, around the central axis of the, stationary scroll 1.
In the Oldham ring 18, as the position of the key is deviated from the ring portion 19 in the thickness direction, if the scroll type fluid machine makes a high speed rotation, the Oldham ring 18 tends to incline by a moment caused by an inertia force Fi (FIG. 7) of the Oldham ring 18 and a reaction force Fd (FIG. 7) acting against said inertia force on the end face of the key way 22 of the swivel side.
The Oldham ring 18 thus reciprocates while it is inclining and making vibrations (hereinafter such vibrations are referred to as "inclining vibrations). But during high speed rotation, as the inertia force Fi of the Oldham ring 18 increases in proportion to the square of the rotation, the moment sharply increases and the Oldham ring 18 increases in inclining vibrations.
As a result, the Oldham ring 18 collides with the end plate 6 of the swivel scroll 2 and with the frame 10, which causes shock sounds. Thus there is a problem that the operation noise of the scroll type fluid machine is increased more and more.
Especially if the flatness of the Oldham ring 18 is not good enough, due to the revolutional swivel motions, being accompanied by conical motions, of the swivel scroll 2 in the compression process: vibrations of the Oldham ring 18 are remarkably increased and intensified; the Oldham ring 18 wears abnormally, seizure occurs between the Oldham ring 18 and the end plate 6 (the swivel scroll 2) or between the Oldham ring 18 and the frame 10; and there is the fear of a fluid machine not operating.
one countermeasure therefor in recent years is disclosed in Japanese laid-open utility model application No. Hei 1(1989) 157201. That is, an allowable inclination of the Oldham ring 18 is restricted by the thickness of the swivel side key 20 and the depth of the key way 22 in which the swivel side key 20 is fitted, another is disclosed in Japanese laid-open utility model application No. Hei 2(1990)-127701. That is, an allowable inclination of the Oldham ring 18 is restricted by the bottom face of the key way 23 in which the stationary side key 21 is fitted and the sliding face of the thrust bearing 11 with which the stationary side key 21 makes sliding contact.
In the above prior art, in order to adjust the thickness of the individual separate key portions, or to control the flatness between the separate key portions, only the individual portion of the key portions or area between the key portions is restricted, There is thus a difficulty in making the thickness adjustment and the flatness control on the whole.
Therefore, a simpler countermeasure is desired.